I am writing a grant application which will be evaluating a new diagnostic test. The test will predict whether a patient with lung fibrosis will remain stable or progress. I am using an existing cohort of patients with lung fibrosis to test this new diagnostic test. I was planning on reporting the results of the diagnostic test as AUC and sensitivity and specificity.
The cohort has 308 patients. 155 are known to have developed progressive disease 153 are known to have remained stable
Based on previous studies, I would expect the diagnostic test to achieve an AUC of at least 0.75 (80% power (α=0.05))
I have been told that I may be asked at interview about power calculations and sample sizes. I have a few questions:
Although this would be a post-hoc sample calculation, does it even make sense to do a power calculation. Would the question "is the population adequately powered to allow an AUC of 0.75?" be a valid question to ask?
I apologise for this very basic question, but I am having great difficulty getting a straight answer (perhaps because my question is incorrect?)